In general, micromechanical pressure sensor elements are formed on a substrate or a chip by forming a diaphragm having a cavity on the top of the substrate or chip by underetching. A measuring device which determines a pressure differential between the cavity and an outer space as a deflection of the diaphragm is formed in the diaphragm, for example by piezoelectric resistors. Pressure sensor elements of this type may be conventionally manufactured using bulk micromechanics or surface micromechanics (SMM).
German Patent Application No. DE 100 32 579 describes a cost-effective manufacturing method for a pressure sensor element manufactured using surface micromechanics, in which coarse pores are initially formed, so that a sponge-like or lattice-like structure is obtained, on which a monocrystalline epitaxial layer is formed and subsequently heat-treated for the later diaphragm, forming a large-volume cavity underneath the diaphragm. This may take place in a protective hydrogen atmosphere which then diffuses from the cavity through the diaphragm, leaving behind a vacuum, so that the diaphragm is exposed to the absolute pressure of the external space.
Pressure sensor elements of this type are generally used for tire pressure measurement by bonding the sensor chip onto a substrate, a printed circuit board, for example, and installing it, for example, in the area of the tire valve. The tire pressure sensor is provided with a dedicated voltage source, in general a galvanic element, and transmits measuring signals or analysis signals derived therefrom to an external receiver in the vehicle via an antenna. However, continuous operation of the tire pressure sensor entails high power consumption, which strongly reduces the service life of the tire pressure sensor.